On Sun, 30 Nov 2003 14:00:40 +1100, "Matt"
wrote:

To the purist, you should use the same impedance cable all the way through,
however in practice, you can get away with using the small run of 75 Ohm
cable. You will incur some additional loss in the system because you are
adding in some additional connectors.
Another option is to redesign the cable run with reagrds to where it
connects to the scanner. In using cable ties you can also take the strain
away from the connector by tying the cable to the bench or cabinet that the
scanner is on.
Alternatively you could look at using a right angle connector from the cable
to the radio.
Lots of options to consider.

On a stub cable length as is being proposed, the losses from the
connectors are likely to be higher then from the cable mismatch.
The loss in the Ghz Range from Coax is huge per 100 feet, but
fortunately 3 feet is only a small fraction of 100 feet.


Every impedance discontinuity is trouble, and the fewer the better.


Matt

"Robert11" wrote in message
...
Hello:

Question on Coax.

I am presently using a 50 foot run of 50 ohm coax to my scanner.

It's the 0.4 inch low-loss diameter stuff (I think LMR 400), and I wanted
to
add a short length of
a coax between this cable and the scanner to remove the strain on the
radio's connector due to the stiffness of
the LMR 400.

All I can find pre-assembled with BNC's is 75 ohm RG59.

It's about a 3 ft length.

a. Think the 3 ft radio-to-75 ohm patch cable, then to the 50 ohm main
cable will cause any "meaningful" loss
due to the Z mismatch ?

b. Would I have been better off using a 3 foot RG58 (50 ohm) patch cable,
even though the RG58 is really lossy around 1 GHz ?

Thanks,
Bob